This invention relates to transistors, particularly field effect transistors (FETs), formed from diamond material and to methods of manufacturing such transistors.
The generation of high frequency (HF) and microwave signals is now mostly based on silicon and gallium arsenide devices. Due to physical limitations, these devices cannot achieve power levels higher than a few hundred watts (depending on the frequency to be amplified) in simple solid-state device configurations. Wide band-gap materials (diamond, SiC, GaN, etc) in principle allow for higher power amplification per unit gate length at microwave frequencies. This is because a larger bias voltage, and hence the voltage amplitude on the microwave signal, can be supported across the transistor channel region over which the current is modulated. In effect, the higher breakdown electric field of a wide band-gap semiconductor is exploited. In microwave power transistors, the ability to support high voltage is particularly desirable, since, generally, power has to be transferred to a relatively high impedance (50Ω) load.
The use of diamond in manufacturing transistors of this kind has been described in the following publications: JP-A-60246627, EP 0 343 963 B1 and US005491348A).
It is an object of the invention to provide an alternative transistor structure and method of manufacture thereof with particular advantages in terms of ease of manufacture and performance.